Several ES6 additions are only available in strict mode. Example:
> SyntaxError: Block-scoped declarations (let, const, function, class) not yet supported outside strict mode
Strict mode was also enabled in a few of our files already, and it is a good thing to have anyway.
* Fix the missing Helper method in the edit command to use Helper.HOME and the correct path assembly method (path.join) instead of joining strings together!
* Use $EDITOR instead of "vi" in the event a user doesn't have "vi" installed or doesn't understand it. Fallback to "vi" in case user doesn't have $EDITOR set.
